Future Anterior Cruciate Ligament Injury Research Articles

Knee Biomechanics During Cutting Maneuvers and Secondary ACL Injury Risk: A Prospective Cohort Study of Knee Biomechanics in 756 Female Elite Handball and Soccer Players.

An athlete who returns to sport after an anterior cruciate ligament (ACL) injury has a substantially high risk of sustaining a new secondary ACL injury. Because ACL injuries most frequently occur during cutting maneuvers, such movements should be at the center of research attention. To investigate whether knee biomechanical parameters during side-step cutting maneuvers differ between female elite athletes with and without a history of ACL injury and to evaluate whether such parameters are associated with future secondary ACL injury. Cohort study; Level of evidence, 2. A total of 756 female elite handball and soccer players, of whom 76 had a history of ACL injury, performed a sport-specific cutting task while 3-dimensional kinematics and kinetics were measured. ACL injuries were registered prospectively over an 8-year follow-up period. Seven knee-specific biomechanical variables were the basis for all analyses. Two-way analyses of variance were applied to assess group differences, whereas logistic regression models served to evaluate associations between the knee-specific variables and future secondary ACL injury. When players with a previous ACL injury performed the cutting maneuver with their ipsilateral leg, they exhibited lower knee abduction angles (mean difference [MD], 1.4°-1.5°; 95% CI, 0.2°-2.9°), lower peak knee flexion moments (MD, 0.33 N·m/kg-1; 95% CI, 0.18-0.48 N·m/kg-1), lower peak knee abduction moments (MD, 0.27 N·m/kg-1; 95% CI, 0.12-0.41 N·m/kg-1), and lower peak knee internal rotation moments (MD, 0.06 N·m/kg-1; 95% CI, 0.01-0.12 N·m/kg-1) compared with injury-free players. When players performed the cut with their contralateral leg, no differences were evident (P < .05). None of the 7 knee-specific biomechanical variables was associated with future secondary ACL injury in players with an ACL injury history (P < .05). Approximately 4 years after ACL injury, female elite team-ball athletes still unloaded their ipsilateral knee during cutting maneuvers, yet contralateral knee loading was similar to that of injury-free players. Knee biomechanical characteristics were not associated with future secondary ACL injury.

What it takes to have a high-grade pivot shift-focus on bony morphology.

Variations in femoral and tibial bony morphology have been associated with higher clinical grading and increased quantitative tibial translation, but not tibial acceleration, during the pivot shift test following anterior cruciate ligament (ACL) injury. The purpose of this study was to determine the impact of femoral and tibial bony morphology, including a measurement influenced by both parameters (the Lateral Tibiofemoral Articular Distance (LTAD)), on the degree of quantitative tibial acceleration during the pivot shift test and rates of future ACL injury. All patients who underwent primary ACL reconstruction from 2014 to 2019 by a senior orthopedic surgeon with available quantitative tibial acceleration data were retrospectively reviewed. All patients underwent a pivot shift examination under anesthesia with a triaxial accelerometer. Measurements of femoral and tibial bony morphology were performed by two fellowship-trained orthopedic surgeons using preoperative magnetic resonance imaging and lateral radiographs. Fifty-one patients were included at a mean follow-up of 4.4years. The mean quantitative tibial acceleration during the pivot shift was 13.8m/s2 (range: 4.9-52.0m/s2). A larger Posterior Condylar Offset Ratio (r = 0.30, p = 0.045), smaller medial-to-lateral width of the medial tibial plateau (r = -0.29, p = 0.041), lateral tibial plateau (r = -0.28, p = 0.042), and lateral femoral condyle (r = -0.29, p = 0.037), and a decreased LTAD (r = -0.53, p < 0.001) significantly correlated with increased tibial acceleration during the pivot shift. Linear regression analysis demonstrated an increase in tibial acceleration of 1.24m/s2 for every 1mm decrease in LTAD. Nine patients (17.6%) sustained ipsilateral graft rupture and 10 patients (19.6%) sustained contralateral ACL rupture. No morphologic measurements were associated with rates of future ACL injury. Increased convexity and smaller bony morphology of the lateral femur and tibia were significantly associated with increased tibial acceleration during the pivot shift. Additionally, a measurement, termed the LTAD, was found to have the strongest association with increased tibial acceleration. Based on the results of this study, surgeons can utilize these measurements to preoperatively identify patients at risk of increased rotatory knee instability. Level IV.

Prelanding Knee Kinematics and Landing Kinetics During Single-Leg and Double-Leg Landings in Male and Female Recreational Athletes.

Biomechanical behavior prior to landing likely contributes to anterior cruciate ligament (ACL) injuries during jump-landing tasks. This study examined prelanding knee kinematics and landing ground reaction forces (GRFs) during single-leg and double-leg landings in males and females. Participants performed landings with the dominant leg or both legs while kinematic and GRF data were collected. Single-leg landings demonstrated less time between prelanding minimal knee flexion and initial ground contact, decreased prelanding and early-landing knee flexion angles and velocities, and increased peak vertical and posterior GRFs compared with double-leg landings. Increased prelanding knee flexion velocities and knee flexion excursion correlated with decreased peak posterior GRFs during both double-leg and single-leg landings. No significant differences were observed between males and females. Prelanding knee kinematics may contribute to the increased risk of ACL injuries in single-leg landings compared with double-leg landings. Future studies are encouraged to incorporate prelanding knee mechanics to understand ACL injury mechanisms and predict future ACL injury risks. Studies of the feasibility of increasing prelanding knee flexion are needed to understand the potential role of prelanding kinematics in decreasing ACL injury risk.

Exploring pre-impact landing kinematics associated with increase and decrease in the anterior cruciate ligament injury risk

This study aimed to explore the single-legged landing kinematics that could lead to increase or decrease in the risk of anterior cruciate ligament (ACL) injury. Immediate pre-impact kinematics at the single-legged landing from 33 healthy young female handball players were evaluated. Thereafter, two-year follow-up for ACL injury incidence was conducted, in which six new ACL injuries in non-dominant leg were registered. The evaluation of pre-impact kinematics across participants was performed first by the principal component analysis to decompose them into the kinematic components (KCs), and then by the linear discrimination analysis (LDA) for a set of KC-scores to obtain important KCs for discriminating injured and non-injured legs. The result of LDA showed that the combination of second major KC (knee flexion/extension angle and angular velocity) and some minor KCs such as torso medial/lateral leaning accurately discriminated the injured and non-injured legs with the error rate of 12.5%. To examine the mechanisms of this discriminative ability, we generated hypothetical pre-impact kinematics in the subspaces spanned by eigenvectors of multiple KCs, and examined relationships between pre-impact kinematics and the corresponding knee valgus torque predicted by the motion-equation-based model. The result showed that the second major KC and the minor KCs representing torso medial/lateral leaning and/or hip adduction/abduction angle, which contributed in LDA to discriminating injured legs, also significantly affected the frontal-plane knee loading patterns. These findings suggested that KC-based postural characterization of the pre-impact landing kinematics and the motion-equation-based knee stress quantification possibly explain the future ACL injury risks of female athletes.

Return-to-Sport Criteria After Anterior Cruciate Ligament Reconstruction Fail to Identify the Risk of Second Anterior Cruciate Ligament Injury.

The incidence of second anterior cruciate ligament (ACL) injury after ACL reconstruction (ACLR) is high in young, active populations. Failure to successfully meet return-to-sport (RTS) criteria may identify adult athletes at risk of future injury; however, these studies have yet to assess skeletally mature adolescent athletes. To determine if failure to meet RTS criteria would identify adolescent and young adult athletes at risk for future ACL injury after ACLR and RTS. The tested hypothesis was that the risk of a second ACL injury after RTS would be lower in participants who met all RTS criteria compared with those who failed to meet all criteria before RTS. Prospective case-cohort (prognosis) study. Laboratory. A total of 159 individuals (age = 17.2 ± 2.6 years, males = 47, females = 112). Participants completed an RTS assessment (quadriceps strength, functional hop tests) and the International Knee Documentation Committee patient survey (0 to 100 scale) after ACLR and were then tracked for occurrence of a second ACL tear. Athletes were classified into groups that passed all 6 RTS tests at a criterion level of 90% (or 90 of 100) limb symmetry and were compared with those who failed to meet all criteria. Crude odds ratios and 95% CIs were calculated to determine if passing all 6 RTS measures resulted in a reduced risk of second ACL injury in the first 24 months after RTS. Thirty-five (22%) of the participants sustained a second ACL injury. At the time of RTS, 26% achieved ≥90 on all tests, and the remaining athletes scored less than 90 on at least 1 of the 6 assessments. The second ACL injury incidence did not differ between those who passed all RTS criteria (28.6%) and those who failed at least 1 criterion (19.7%, P = .23). Subgroup analysis by graft type also indicated no differences between groups (P > .05). Current RTS criteria at a 90% threshold did not identify active skeletally mature adolescent and young adult athletes at high risk for second ACL injury.

Descriptive trunk kinematics in healthy collegiate women's soccer players indicate trunk center of mass is laterally positioned prior to decelerating and cutting

ObjectivesTrunk kinematics can contribute to lower extremity biomechanical risk factors for anterior cruciate ligament (ACL) injury. However, normative trunk kinematics during unilateral athletic tasks in a large population of “healthy” (no history of ACL injury and no known future ACL injury) women's soccer players have not been well-described. This study's purposes were to describe trunk kinematics in a population of 37 healthy collegiate women's soccer players completing a step-down, a deceleration, and a 90° cut, and to provide a reference for normative values. MethodsA cross-sectional cohort of 37 female soccer players were analysed for this study. Trunk forward flexion and lateral flexion were measured relative to the pelvis, and trunk centre of mass position was measured relative to the proximal tibia. Trunk kinematics were characterized by individual values at key events during the tasks and time-series curves normalized to 100% of the time. ResultsParticipants demonstrated increasing trunk forward flexion with increasing knee flexion angle, small amounts of increasing ipsilateral trunk flexion with increasing peak knee abduction moment, and trunk centre of mass position that moved medially during the deceleration and cut tasks. Additionally, participants demonstrated peak trunk lateral flexion angles milliseconds before peak knee flexion angle. ConclusionThis study provides a reference for identifying aberrant trunk mechanics that may increase the risk for non-contact ACL injury. Level of evidenceLevel II.

Strength and Biomechanical Risk Factors for Noncontact ACL Injury in Elite Female Footballers: A Prospective Study.

This study aimed to determine if a preseason field-based test battery was prospectively associated with noncontact anterior cruciate ligament (ACL) injury in elite female footballers. In total, 322 elite senior and junior female Australian Rules Football and soccer players had their isometric hip adductor and abductor strength, eccentric knee flexor strength, countermovement jump (CMJ) kinetics, and single-leg hop kinematics assessed during the 2019 preseason. Demographic and injury history details were also collected. Footballers were subsequently followed for 18 months for ACL injury. Fifteen noncontact ACL injuries occurred during the follow-up period. Prior ACL injury (odds ratio [OR], 9.68; 95% confidence interval (95% CI), 2.67-31.46), a lower isometric hip adductor to abductor strength ratio (OR, 1.98; 95% CI, 1.09-3.61), greater CMJ peak take-off force (OR, 1.74; 95% CI, 1.09-3.61), and greater single-leg triple vertical hop average dynamic knee valgus (OR, 1.97; 95% CI, 1.06-3.63) and ipsilateral trunk flexion (OR, 1.60; 95% CI, 1.01-2.55) were independently associated with an increased risk of subsequent ACL injury. A multivariable prediction model consisting of CMJ peak take-off force, dynamic knee valgus, and ACL injury history that was internally validated classified ACL injured from uninjured footballers with 78% total accuracy. Between-leg asymmetry in lower limb strength and CMJ kinetics were not associated with subsequent ACL injury risk. Preseason field-based measures of lower limb muscle strength and biomechanics were associated with future noncontact ACL injury in elite female footballers. These risk factors can be used to guide ACL injury screening practices and inform the design of targeted injury prevention training in elite female footballers.

ACL Rehabilitation: How Can We Lessen Injury Rates?

Rehabilitation is commonly used following anterior cruciate ligament (ACL) injury, though specific protocols are widely varied. Regardless of whether the injury is managed operatively or nonoperatively, quadriceps strengthening and return to full range of motion are the main focus points of rehabilitation, both to regain function and prevent future injury. Preoperative ACL rehabilitation has been shown to improve clinical outcomes. Home exercise programs can also provide good clinical outcomes when compared to traditional in-person physical therapy. A multitude of specific modalities (bracing, functional testing, neuromuscular training, electrostimulation, cryotherapy, and blood flow restriction therapy) may also provide benefit in ACL rehabilitation. Analysis of biomechanics during rehabilitation allows for customization of rehabilitation approaches, provides insight on muscular deficiencies, and helps ACL-injured patients re-establish functionality with the goal of preventing future ipsilateral or contralateral injury. Given the lack of consensus on rehabilitation protocols following ACL injury, the purpose of this review was to examine the efficacy of a variety of protocols and specific modalities and discuss their roles in the prevention of future ACL injury.

Risk of Anterior Cruciate Ligament Injury in Female Soccer Athletes: A Review

Soccer is becoming an increasingly popular sport amongst women. Common movements during play, such as jumping and cutting, require rapid acceleration and deceleration of multiple lower-limb joints. The anterior cruciate ligament (ACL), which contributes to stabilization of the knee, is often injured during these events. ACL injury typically requires costly surgery, extended time away from sports, and jeopardizes long-term joint health. Due to sex-specific factors such as menstruation and anatomical disadvantages, women are more susceptible to tearing their ACL. Injury often occurs in non-contact scenarios during rapid acceleration or deceleration movements. Research has examined these movements and established several kinematic and kinetic mechanisms as well as muscle activation patterns that frequently occur at the time of injury, however results tend to vary based on population. This article summarizes recent and relevant literature of ACL injury mechanisms and highlights the lack of specific research in the high-risk female soccer athlete population. Due to inconclusive risk factors, injury prevention programs within this population have been inconsistent. ACL injury risk for female soccer athletes should be closer examined so that more specific injury risks can be established, and effective protective measures can be taken. Raised awareness of this need may capture attention in the research and medical communities and potentially stimulate the development of strategies that limit future ACL injury and thus the challenges it brings to the high-risk female soccer athlete.

Risk of Anterior Cruciate Ligament Injury in Female Soccer Athletes: A Review

Soccer is becoming an increasingly popular sport amongst women. Common movements during play, such as jumping and cutting, require rapid acceleration and deceleration of multiple lower-limb joints. The anterior cruciate ligament (ACL), which contributes to stabilization of the knee, is often injured during these events. ACL injury typically requires costly surgery, extended time away from sports, and jeopardizes long-term joint health. Due to sex-specific factors such as menstruation and anatomical disadvantages, women are more susceptible to tearing their ACL. Injury often occurs in non-contact scenarios during rapid acceleration or deceleration movements. Research has examined these movements and established several kinematic and kinetic mechanisms as well as muscle activation patterns that frequently occur at the time of injury, however results tend to vary based on population. This article summarizes recent and relevant literature of ACL injury mechanisms and highlights the lack of specific research in the high-risk female soccer athlete population. Due to inconclusive risk factors, injury prevention programs within this population have been inconsistent. ACL injury risk for female soccer athletes should be closer examined so that more specific injury risks can be established, and effective protective measures can be taken. Raised awareness of this need may capture attention in the research and medical communities and potentially stimulate the development of strategies that limit future ACL injury and thus the challenges it brings to the high-risk female soccer athlete.

Kiss goodbye to the ‘kissing knees’: no association between frontal plane inward knee motion and risk of future non-contact ACL injury in elite female athletes

ABSTRACT The aim of this study was to investigate if frontal plane knee and hip control in single-leg squats or vertical drop jumps with an overhead target were associated with future non-contact anterior cruciate ligament (ACL) injury in elite female athletes. Of the 429 handball and 451 football athletes (age 21.5 ± 4.0 years, height 169.6 ± 6.4 cm, body weight 67.1 ± 8.0 kg), 722 non-injured and 56 non-contact ACL injured participants were eligible for analysis. We calculated lateral pelvic tilt, frontal plane knee projection angle, medial knee position, and side-to-side asymmetry in these from 2D videos recorded at baseline, and recorded any new ACL injuries prospectively. None of the aforementioned variables in either screening task were different or could discriminate between injured and non-injured athletes (all p values >.05 and Cohen’s d values < .27). Two-dimensional video assessment of frontal plane knee and hip control during both a single-leg squat and vertical drop jump was unable to identify individuals at increased risk of non-contact ACL injury, thus should not be used for screening.

Poor Validity of Functional Performance Tests to Predict Knee Injury in Female Soccer Players With or Without Anterior Cruciate Ligament Reconstruction

Background: Various tests have been developed to evaluate athletes’ functional performance and for use as screening tools for injury prediction. Further validation of their accuracy to predict injury is needed. Purpose: To investigate the validity of predetermined cutoffs used to differentiate between high- and low-risk players in different functional performance tests to predict (1) anterior cruciate ligament (ACL) injury or (2) severe traumatic knee injury in a cohort of female soccer players with a primary unilateral ACL reconstruction and a cohort of knee-healthy players. Study Design: Cohort study; Level of evidence, 2. Methods: A total of 117 active female soccer players (mean age ± SD, 20 ± 2 years) an average of 19 ± 9 months after ACL reconstruction and 119 knee-healthy players (age, 19 ± 3 years) were prospectively followed up for 2 years for new knee injuries. At baseline, all players underwent tests to assess postural control (Star Excursion Balance Test), hop performance (single-leg hop for distance, side hop), and movement asymmetries in the lower limbs and trunk (drop vertical jump [DVJ], tuck jump). The predictive validity of the test cutoffs to identify players who would sustain an ACL injury or a severe traumatic knee injury (absence from soccer play, >28 days) was assessed. The risk ratio (RR), area under the receiver operating characteristic curve (AUC), sensitivity, and specificity were calculated. Results: A total of 46 players (39%) with ACL reconstruction sustained 48 severe knee injuries, including 28 ACL ruptures. Of the knee-healthy players, 13 (11%) sustained 14 severe knee injuries, including 8 ACL ruptures. No association was found between the predetermined functional performance test cutoffs and the risk of a new ACL injury or severe knee injury in players with ACL reconstruction. In knee-healthy players, the only variable associated with future ACL injury was ≥6.5 cm knee valgus in the frontal plane (any knee) in the DVJ (RR, 4.93; 95% CI, 1.04-23.40; P = .045), but with only fair predictive validity (AUC, 0.7; sensitivity, 0.75; specificity, 0.65). Conclusion: In our cohorts of female soccer players, the validity of commonly used functional performance tests to predict new knee injuries was poor. Only knee valgus during the DVJ was associated with new ACL injuries in knee-healthy players, but with only fair predictive validity.

Does delayed onset muscle soreness affect the biomechanical variables of the drop vertical jump that have been associated with increased ACL injury risk? A randomised control trial.

Delayed onset muscle soreness (DOMS) and Anterior Cruciate Ligament (ACL) injuries are both prevalent in sport. It is currently unknown whether DOMS increases ACL injury risk. This study aimed to provide preliminary insight on whether DOMS affects ACL injury risk by investigating whether DOMS affects the biomechanical variables of the DVJ that have been identified as risk factors for future ACL injury. This was a randomised control trial involving 32 active individuals aged 18-35years, with no history of ACL injury. Participants underwent two sessions of force-plate testing and 3D motion analysis of the drop vertical jump (DVJ). The DVJ was chosen as it has been investigated prospectively for association with future ACL injury. Initial testing was followed by randomisation to DOMS or control group. The DOMS group underwent a DOMS-inducing exercise protocol, the control group did not. Both groups were re-tested 48h after initial testing. Five variables of the DVJ that have been associated with future ACL injury were chosen for analysis - peak knee flexion angle, peak vertical ground reaction force, ground contact time, peak knee abduction angle & peak knee abduction moment. Between-group differences were compared using a two-way mixed analysis of variance; alpha level set to 0.05. DOMS was successfully induced in all participants of the DOMS group however no statistically significant group x time interactions were found for any of the five variables analysed. DOMS did not affect the biomechanical variables of the DVJ that have been associated with future ACL injury. By extension, this may suggest that DOMS might not affect ACL injury risk. However, it is also possible that certain attributes of the DVJ meant that any effect of DOMS was simply unable to be quantified, even if an effect existed. All considered, our position is that conclusion cannot be drawn from this study alone on whether DOMS affects ACL injury risk. Further research is required.

Can Biomechanical Testing After Anterior Cruciate Ligament Reconstruction Identify Athletes at Risk for Subsequent ACL Injury to the Contralateral Uninjured Limb?

Background: Athletes are twice as likely to rupture the anterior cruciate ligament (ACL) on their healthy contralateral knee than the reconstructed graft after ACL reconstruction (ACLR). Although physical testing is commonly used after ACLR to assess injury risk to the operated knee, strength, jump, and change-of-direction performance and biomechanical measures have not been examined in those who go on to experience a contralateral ACL injury, to identify factors that may be associated with injury risk. Purpose: To prospectively examine differences in biomechanical and clinical performance measures in male athletes 9 months after ACLR between those who ruptured their previously uninjured contralateral ACL and those who did not at 2-year follow-up and to examine the ability of these differences to predict contralateral ACL injury. Study Design: Case-control study; Level of evidence, 3. Methods: A cohort of male athletes returning to level 1 sports after ACLR (N = 1045) underwent isokinetic strength testing and 3-dimensional biomechanical analysis of jump and change-of-direction tests 9 months after surgery. Participants were followed up at 2 years regarding return to play or at second ACL injury. Between-group differences were analyzed in patient-reported outcomes, performance measures, and 3-dimensional biomechanics for the contralateral limb and asymmetry. Logistic regression was applied to determine the ability of identified differences to predict contralateral ACL injury. Results: Of the cohort, 993 had follow-up at 2 years (95%), with 67 experiencing a contralateral ACL injury and 38 an ipsilateral injury. Male athletes who had a contralateral ACL injury had lower quadriceps strength and biomechanical differences on the contralateral limb during double- and single-leg drop jump tests as compared with those who did not experience an injury. Differences were related primarily to deficits in sagittal plane mechanics and plyometric ability on the contralateral side. These variables could explain group membership with fair to good ability (area under the curve, 0.74-0.80). Patient-reported outcomes, limb symmetry of clinical performance measures, and biomechanical measures in change-of-direction tasks did not differentiate those at risk for contralateral injury. Conclusion: This study highlights the importance of sagittal plane control during drop jump tasks and the limited utility of limb symmetry in performance and biomechanical measures when assessing future contralateral ACL injury risk in male athletes. Targeting the identified differences in quadriceps strength and plyometric ability during late-stage rehabilitation and testing may reduce ACL injury risk in healthy limbs in male athletes playing level 1 sports. Clinical Relevance: This study highlights the importance of assessing the contralateral limb after ACLR and identifies biomechanical differences, particularly in the sagittal plane in drop jump tasks, that may be associated with injury to this limb. These factors could be targeted during assessment and rehabilitation with additional quadriceps strengthening and plyometric exercises after ACLR to potentially reduce the high risk of injury to the previously healthy knee. Registration: NCT02771548 (ClinicalTrials.gov identifier).

Do knee abduction kinematics and kinetics predict future anterior cruciate ligament injury risk? A systematic review and meta-analysis of prospective studies

BackgroundTo systematically review the association between knee abduction kinematics and kinetics during weight-bearing activities at baseline and the risk of future anterior cruciate ligament (ACL) injury.MethodsSystematic review and meta-analysis according to PRISMA guidelines. A search in the databases MEDLINE (PubMed), CINAHL, EMBASE and Scopus was performed. Inclusion criteria were prospective studies including people of any age, assessing baseline knee abduction kinematics and/or kinetics during any weight-bearing activity for the lower extremity in individuals sustaining a future ACL injury and in those who did not.ResultsNine articles were included in this review. Neither 3D knee abduction angle at initial contact (Mean diff: -1.68, 95%CI: − 4.49 to 1.14, ACL injury n = 66, controls n = 1369), peak 3D knee abduction angle (Mean diff: -2.17, 95%CI: − 7.22 to 2.89, ACL injury n = 25, controls n = 563), 2D peak knee abduction angle (Mean diff: -3.25, 95%CI: − 9.86 to 3.36, ACL injury n = 8, controls n = 302), 2D medial knee displacement (cm; Mean diff:: -0.19, 95%CI: − 0,96 to 0.38, ACL injury n = 72, controls n = 967) or peak knee abduction moment (Mean diff:-10.61, 95%CI: - 26.73 to 5.50, ACL injury n = 54, controls n = 1330) predicted future ACL injury.ConclusionContrary to clinical opinion, our findings indicate that knee abduction kinematics and kinetics during weight-bearing activities may not be risk factors for future ACL injury. Knee abduction of greater magnitude than that observed in the included studies as well as factors other than knee abduction angle or moment, as possible screening measures for knee injury risk should be evaluated in future studies.

Current Return to Sport Criteria after ACL Reconstruction Fail to Identify Increased Risk of Second ACL Injury in Young Athletes

Objectives:The incidence of 2nd anterior cruciate ligament (ACL) injury after ACL reconstruction (ACLR) and return to sport (RTS) ranges from 25%-33% in young, active populations; with the greatest risk in the first 12 months after RTS. Recent data indicate that failure to successfully meet traditional RTS criteria, inclusive of strength, functional hop testing and patient reported outcome scores, may identify athletes at increased risk of future injury after ACLR. However, these studies have focused on adult populations and it is unknown if similar RTS criteria apply to young, adolescent, pivoting/cutting athletes. The purpose of this study was to determine if meeting all current, standard RTS criteria would identify young athletes at risk for future ACL injury after primary ACLR and RTS. The tested hypothesis was the likelihood of 2nd ACL injury in the first 2 years after RTS would be lower in patients who met all RTS criteria prior to initiation of pivoting and cutting activity compared to patients who failed to meet all RTS criteria prior to RTS.Methods:One hundred fifty-nine subjects (112 female, 47 male) with a mean age of 17.2±2.6 years old (range: 13-25 y.o.) underwent ACLR and were released to return to pivoting/cutting sport. These patients were enrolled in a prospective, observational cohort study, completed a RTS assessment and were then tracked for occurrence of 2nd ACL after ACLR for 24 months. The RTS assessment included 6 tests: isometric quadriceps strength, 4 functional hop tests and the International Knee Documentation Committee (IKDC) patient reported outcome survey. Limb symmetry index (LSI) was calculated for strength and hop test assessments [(involved/uninvolved)*100]. The IKDC was reported on a 0-100 scale with 100 representing a perfect score. Subjects were classified into groups that successfully passed all 6 RTS tests at a level of 90 and again at 95 compared to those that failed to meet all 6 criteria. Chi Square tests were used to determine if successfully passing all 6 RTS measures at various levels of symmetry resulted in a reduced risk of 2nd ACL injury in the first 24 months after RTS.Results:Thirty-five (22.0%) patients suffered a 2nd ACL injury, with 26 occurring in the first 12 months after RTS. At the time of RTS, 42 patients (26%) achieved LSI values of 90 or greater on all testing as well as an IKDC value of 90 or greater. The remaining 117 subjects (74%) scored below 90 on at least 1 of the 6 assessments. At this level, there was no difference in 2nd ACL injury prevalence between patients who passed all RTS criteria (12/42; 28.6%) and those who failed at least 1 criteria (23/117; 19.7%) (p=0.23). When the passing criteria was elevated to 95 on all RTS testing, only 15 subjects (9%) successfully passed all 6 tests. There was no significant difference in 2nd ACL injury prevalence between patients who passed all RTS criteria (5/15; 33%) and those who failed at least 1 test (30/144; 20.8%) (p=0.32). Sub-group analysis which evaluated the group by graft type, also indicated no significant differences between groups (p>0.05).Conclusion:Current criteria to evaluate readiness to return young athletes to pivoting and cutting sports, using quadriceps strength symmetry, functional hop performance symmetry and patient reported outcomes, may not identify young, active patients at high risk for 2nd ACL injury. Future work must identify more appropriate criteria to assess readiness to RTS in the young, athletic population and incorporate these findings into practice.

Drop-Jump Landing Varies With Baseline Neurocognition

Background: Neurocognitive status may be a risk factor for anterior cruciate ligament (ACL) injury. Neurocognitive domains such as visual attention, processing speed/reaction time, and dual-tasking may influence ACL injury risk via alterations to neuromuscular performance during athletic tasks. However, the relationship between neurocognition and performance during athletic tasks is not yet established. Hypothesis: Athletes with low baseline neurocognitive scores will demonstrate poorer jump landing performance compared with athletes with high baseline neurocognitive score. Study Design: Controlled laboratory study. Methods: Neurocognitive performance was measured using the Concussion Resolution Index (CRI). Three-dimensional kinematic and kinetic data of the dominant limb were collected for 37 recreational athletes while performing an unanticipated jump-landing task. Healthy, nonconcussed subjects were screened using a computer-based neurocognitive test into a high performers (HP; n = 20; average CRI percentile, 78th) and a low performers (LP; n = 17; average CRI percentile, 41st) group. The task consisted of a forward jump onto a force plate with an immediate rebound to a second target that was assigned 250 milliseconds before landing on the force plate. Kinematic and kinetic data were obtained during the first jump landing. Results: The LP group demonstrated significantly altered neuromuscular performance during the landing phase while completing the jump-landing task, including significantly increased peak vertical ground-reaction force (mean ± SD of LP vs HP: 1.81 ± 0.53 vs 1.38 ± 0.37 body weight [BW]; P < .01), peak anterior tibial shear force (0.91 ± 0.17 vs 0.72 ± 0.22 BW; P < .01), knee abduction moment (0.47 ± 0.56 vs 0.03 ± 0.64 BW × body height; P = .03), and knee abduction angle (6.1° ± 4.7° vs 1.3° ± 5.6°; P = .03), as well as decreased trunk flexion angle (9.6° ± 9.6° vs 16.4° ± 11.2°; P < .01). Conclusion: Healthy athletes with lower baseline neurocognitive performance generate knee kinematic and kinetic patterns that are linked to ACL injury. Clinical Relevance: Neurocognitive testing using the CRI may be useful for identification of athletes at elevated risk for future ACL injury.

Hip Muscle Strength Predicts Noncontact Anterior Cruciate Ligament Injury in Male and Female Athletes

Background: Prospective studies have reported that abnormal movement patterns at the trunk, hip, and knee are associated with noncontact anterior cruciate ligament (ACL) injuries. Impaired hip strength may underlie these abnormal movement patterns, suggesting that diminished hip strength may increase the risk of noncontact ACL injury. Purpose: To determine whether baseline hip strength predicts future noncontact ACL injury in athletes. Study Design: Case-control study; Level of evidence, 3. Methods: Before the start of the competitive season, isometric hip strength (external rotation and abduction) was measured bilaterally by use of a handheld dynamometer in 501 competitive athletes (138 female and 363 male athletes) participating in various sports. During the sport season, ACL injury status was recorded, and injured athletes were further classified based on the mechanism of injury (noncontact vs contact). After the season, logistic regression was used to determine whether baseline hip strength predicted future noncontact ACL injury. Receiver operating characteristic (ROC) curves were constructed independently for each strength measure to determine the clinical cutoff value between a high-risk and low-risk outcome. Results: A total of 15 noncontact ACL injuries were confirmed (6 females, 9 males), for an overall annual incidence of 3.0% (2.5% for males, 4.3% for females). Baseline hip strength measures (external rotation and abduction) were significantly lower in injured athletes compared with noninjured athletes (P = .003 and P < .001, respectively). Separate logistic regression models indicated that impaired hip strength increased future injury risk (external rotation: odds ratio [OR] = 1.23 [95% CI, 1.08-1.39], P = .001; abduction: OR = 1.12 [95% CI, 1.05-1.20], P = .001). Clinical cutoffs to define high risk were established as external rotation strength ≤20.3% BW (percentage of body weight) or abduction strength ≤35.4% BW. Conclusion: Measures of preseason isometric hip abduction and external rotation strength independently predicted future noncontact ACL injury status in competitive athletes. The study data suggest that screening procedures to assess ACL injury risk should include an assessment of isometric hip abduction and/or external rotation strength.

Utilization of ACL Injury Biomechanical and Neuromuscular Risk Profile Analysis to determine the effectiveness of Neuromuscular Training

Objectives:Over 125,000 anterior cruciate ligament (ACL) injuries occur each year in the United States. External loads on the knee in the frontal plane, specifically the knee abduction moment (KAM), predict future ACL injury with high sensitivity and specificity. The purpose of this randomized controlled trial (RCT) was to determine if biomechanical and neuromuscular factors could be used to characterize athletes by distinct factor profiles, to examine if neuromuscular training (NMT) would decrease the potential risk factors, and if NMT would preferentially benefit athletes that exhibited specific risk profiles. The hypotheses tested were: 1) a priori chosen biomechanical and neuromuscular factors would characterize subjects into distinct at-risk profiles, 2) NMT would decrease biomechanical and neuromuscular factors related to increased injury risk and 3) the decrease in these biomechanical and neuromuscular factors would be greater in those athletes characterized by the overall higher risk profiles.Methods:A total of 624 female athletes from 52 basketball, soccer and volleyball teams participated and were screened prior to their competitive season. During the pre-season testing, the athletes performed 3 different types of tasks for which biomechanical measures were taken: 1) drop vertical jump (DVJ), 2) single leg drop (SLD), and 3) single leg cross drop (SCD) landings. Using data from these tasks a latent profile analysis (LPA) was conducted to identify distinct profiles based on pre-intervention biomechanical and neuromuscular measures. As a validation, we examined whether the profile membership was significant predictor of KAM. Analysis of Co-Variance (ANCOVA) was used to examine treatment effects of NMT on biomechanical and neuromuscular measures in the 375 athletes who completed both pre- and post-intervention tasks. Differences were considered statistically significant at p<0.05.Results:LPA using six pre-intervention biomechanical measures selected a priori resulted in three distinct profiles. Athletes in profiles II and III had significant higher KAM, compared to Profile I. The Core/Trunk-based NMT significantly increased hip external rotation moments and moment impulse and increased peak trunk flexion and decreased extension. In addition, the treatment effect of NMT varied by pre-intervention risk profile. Athletes with pre-intervention risk Profile II and III (higher risk) had a more significant treatment effect of NMT than Profile I.Conclusion:This is the first study to use LPA analysis of biomechanical landing data to create KAM and potentially ACL injury risk profiles. The LPA of multiple biomechanical and neuromuscular measures identified three distinct risk groups; associated with differences in peak KAM Analysis of the RCT showed that NMT significantly increased hip external rotation moments and moment impulse and increased peak trunk flexion and decreased extension, and that alterations in risk factors are different across risk profile group, with higher risk groups showing an overall significant improvement in KAM. These findings show the existence of discernable groups of athletes that are more appropriate for NMT intervention; further study is needed in even larger cohorts to investigate ACL injury as our primary outcome variable.

Deficits in Hip-Ankle Coordination in Female Athletes who Suffer a Second Anterior Cruciate Ligament (ACL) Injury after ACL Reconstruction and Return to Sport

Objectives:Athletes who return to sport after ACL reconstruction (ACLR) are at increased risk of future ACL injury. Proprioceptive deficits at the knee, known to be present at thetime of ACL injury, may persist for up to 2 years after ACLR. Coordinated movements of the hip and ankle are critical in the absence of normal knee proprioception during dynamic athletic movements. Failure to optimally position the knee may make the passive structures susceptible to pathologic stresses that increase the risk of subsequent ligament or graft failure. The purpose of this work was to prospectively determine if altered lower extremity coordination patterns exist in female athletes, who go on to suffer a second ACL injury to either limb, after ACLR and return to sport (RTS). The study tested the hypothesis that female athletes who sustained a second ACL injury would demonstrate altered lower extremity coordination patterns indicative of persistent neuromuscular deficits at the time of return to sport compared to female athletes who would not subsequently sustain a second ACL injury.Methods:Sixty-one female athletes, who sustained an ACL injury, underwent ACLR, completed rehabilitation and were medically cleared for RTS were enrolled in this study. Hip-ankle coordination was assessed on all athletes prior to RTS as they performed a dynamic postural coordination task. The task required participants to stand on a single leg and track the anterior-posterior (AP) movement of an oscillating 3-D square target displayed on a computer monitor. Participants tracked the target with the head so as to maintain a constant perceived distance between their head and the target by matching the amplitude and frequency of the target oscillations. Fourteen patients sustained a second ACL injury within 12 months of RTS (ACLR2). Fourteen matched subjects after ACLR, who did not suffer a second ACL injury (ACLR1), were selected for comparative analysis. Cross-recurrence quantification analysis (Figure 1) was used to characterize hip-ankle coordination patterns through the variable cross-maxline (CML). A group (ACLR1 vs. ACLR2) X target speed (slow vs. fast) X leg (affected vs. unaffected) mixed-model analysis of variance was used to identify coordination differences.Results:A significant main effect of group was observed (p = 0.02), and indicated that the ACLR1 group exhibited more stable hip-ankle coordination overall (M = 166.2 ± 18.9) compared to the ACLR2 group (M = 108.4 ± 10.1), irrespective of target speed or tested leg. A leg x group interaction was also observed (p = .04). A Mann-Whitney test was employed due to unequal variances between groups, and indicated that the affected leg of the ACLR1 group exhibited more stable coordination (M = 187.1 ± 23.3)compared to the affected leg of the ACLR2 group (M = 110.13 ± 9.8), p = 0.03.Conclusion:Hip-ankle coordination was altered in female athletes who subsequently sustain a second ACL injury after initial ACLR and RTS. Failure to appropriately coordinate lower extremity movement between the adjoining proximal and distal hip and ankle in the absence of normal knee proprioception, may place the knee in a high-risk position and increase the likelihood of a second ACL injury in this population.